Natural analog system for reducing permeability of ground

ABSTRACT

A method of chemically and physically treating unconsolidated soils, overburden, fill and certain waste materials (the “ground”), or partly consolidated materials that can be excavated and broken up by normal earth moving and soil mixing equipment. This treatment results in the reduction of permeability in the ground, and as a result permits the prevention or control of contaminant migration from a site containing ground wastes of various types, thereby isolating these wastes.

FIELD OF THE INVENTION

This invention pertains to a system for the reduction of permeability inunconsolidated soils, over burden, fill and certain waste materials (the“ground”), or partly consolidated materials that can be excavated andbroken up by normal earth moving and soil mixing equipment. The systempermits the prevention or control of contaminant migration viagroundwater flow or surface water (precipitation) infiltration from asite containing ground wastes (other than garbage) of various types,thereby isolating these wastes. In some applications the system may alsoincrease the cohesion and mechanical strength of unconsolidated ground.

BACKGROUND OF THE INVENTION

In nature, the lithification of unconsolidated materials commonly occursby the infilling of intergranular void space with interstitial materialdeposited from solution as mineral overgrowths and cements. This loss ofvoid space progressively decreases the primary permeability could reduceit to insignificance. A close natural analog of the Natural AnalogSystem (NAS) is the formation of “caliche” soils in the southwesternUnited States desert regions. Such regions are typically characterizedby dry lake beds that are progressively cemented by salts precipitatedfrom the occasional run-off precipitation which reaches the lake basinand then evaporates.

Another example of a natural analog of the NAS is the formation of lowpermeability “hard pan” soil zones caused by precipitation of cement viaground water evaporation at the sub-surface water table interface. Themost common precipitate cement in these examples are calcium carbonate(CaCO₃) and various forms of silica (Si0₂ or SiO_(X)(H₂O)_(y)) ascompatible in ambient alkaline or acid environments, respectively. Mostground waters, however, are neutral to alkaline (pH>7.0). NAS isprimarily designed for this situation.

The NAS process follows the same principle of reducing void space toreduce permeability by artificially stimulating or inducing void spacefilling via interstitial precipitation, crystallization, and addition ofparticulates plus or minus cementation to duplicate that naturalprocess, but much faster.

Related methods of treatment of ground strata include U.S. Pat. No.4,869,621, issued on Sep. 26, 1989 to McLaren et al. for METHOD OFSEALING PERMEABLE EARTH SURFACE OR SUBSURFACE MATERIALS HAVING ALKALINECONDITIONS BY INDUCED PRECIPITATION OF CARBONATES. McLaren et al.propose a method of artificially sealing voids in earth strata underalkaline conditions by inducing precipitation, via pumped slurries ofaqueous solutions which may include finely divided solids, for example,of calcium carbonate, usually in the form of calcite.

U.S. Pat. No. 4,981,394, issued on Jan. 1, 1991 to McLaren et al. forMETHOD OF SEALING PERMEABLE UNCONSOLIDATED MATERIALS. McLaren et al.propose a method for forming solid layers or local zones of materialupon or below the earth's surface and above the water table to inhibitthe flow of groundwaters through such layers of materials.

The NAS process is a method of precipitating calcium carbonate cement inthe ground that duplicates natural geologic cementing mechanisms.Calcium carbonate, the artificially produced product of the process, isanalogous to the naturally produced calcium carbonate cements ofsedimentary rock. A significant potential use, among several, of the NASprocess is to reduce or eliminate ground water flow-though incontaminated soils and rocks, and thereby immobilize and isolate suchsources of contamination in the natural environment. A principaladvantage of the NAS process in environmental remediation andengineering applications is that the cement (calcite) is a naturalanalog the permanence of which can be established by comparison withsimilar naturally cal cite-cemented geologic materials. The NAS processintroduces the concept of using such natural analog materials inenvironmental remediation and restoration projects rather than usingartificial materials. Such artificial materials can not be assessed interms of very long-term performance of the projects in various geologicsettings.

The principal advantage of the NAS process when used in environmentalremediations and restorations is that it can be applied by fluidinjection in situ, that is, without excavation and processing of thecontaminated-site soil or rock. A contaminated site can be isolated fromthe ambient ground water and immobilized as a source of hydrologicallytransported chemical species, without disturbance of surrounding terrainor structures. Further, the subsequent long-term performance of theremediated site can be determined by comparison with naturally occurringcarbonate-cemented sites. Where appropriate, the NAS process can beapplied by physically mixing NAS process components in contaminated soiland waste material to achieve remediation.

An important aspect of the NAS process is the induced precipitation ofancillary compounds that bind or capture hazardous chemical species fromground water or directly from the waste associated with a contaminatedsite. Such compounds are analogs of minerals known to be stable(insoluble) in such hydrogeologic conditions. The result is theimmobilization of various hazardous chemical species (e.g., lead) intoartificial minerals, the subsequent long-term environmental permanenceof which can be documented by comparison with the equivalent naturallyoccurring minerals.

It is an object of this invention to reduce and/or eliminate soil/rockpermeability and achieve isolation from ground water flow/pathways inland-fill, hazardous and toxic waste-site, and radioactive waste-siteremediation.

SUMMARY OF THE INVENTION

One aspect of the present invention provides a method of enhancing a useof a Natural Analog System (NAS), the steps comprising: a) analyzingwaste in a waste zone to identify chemical constituents for whichimmobilization is particularly desirable; b) impregnating said wastezone with a known increment of a suitable solution equal to or greaterthan the calculated amount required to react with said chemicalconstituents, wherein the suitable solution comprises iron in solution;c) selectively immobilizing the chemical constituents of the waste asinsoluble sols formed from said chemical constituents and the suitablesolutions; and d) repeating steps a-c until refusal occurs.

A second aspect of the present invention provides a method of using aNatural Analog System (NAS) to reduce the permeability of an acidicwaste zone, comprising: impregnating the waste zone with analkali-silicate or metasilicate solution, filling pore space in anunderlayer of the waste zone and reducing permeability and transmissionof fluids in the underlayer of the waste zone because of the reducedpore space; and repeating the impregnating step until refusal occurs.

A third aspect of the present invention provides a method of using theNatural Analog System (NAS) to reduce the permeability of ground,wherein said ground contains wastes such that the pH of said ground isacidic, and wherein said ground lies within a saturated waste zone, thesteps comprising: a) impregnating the waste zone with a composition toproduce gelation, filling pore space, said composition comprising anaqueous alkali-silicate or metasilicate solution; b) adding a suitablegelling agent at the point of said solution introduction, therebyinducing gelation, producing silica gel; and c) repeating saidimpregnating step (a) until refusal occurs.

A fourth aspect of the present invention provides a method of enhancingthe use of the Natural Analog System (NAS) to reduce the permeability ofground, wherein certain chemical constituents of the waste areselectively immobilized, producing insoluble reaction products betweensaid chemical constituents and suitable solutions, the steps comprising:a) analyzing waste to identify chemical constituents for whichimmobilization is particularly desirable; and b) impregnating said wastewith a known increment of said suitable solutions equal to or greaterthan the calculated amount required to react with said chemicalconstituents forming insoluble reaction products.

BRIEF DESCRIPTION OF THE DRAWINGS

A complete understanding of the present invention may be obtained byreference to the accompanying drawings, when considered in conjunctionwith the subsequent detailed description, in which:

FIG. 1 depicts a graph of test results on a first sample in accordancewith embodiments of the invention;

FIG. 2 depicts a graph of test results on a second sample in accordancewith the embodiments of the invention;

FIG. 3 depicts a moisture-density (i.e., Proctor) curve showing therelationship between the dry unit weight (density) and the water contentof the waste material for a given compactive effort in accordance withembodiments of the invention; and

FIG. 4 depicts STATE OF CONSOLIDATION OF GROUND following impregnation(f), (g), or (h) in accordance with embodiments of the invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

In accordance with the present invention, there is provided a method ofusing the Natural Analog System (NAS) to reduce the permeability ofground. A waste zone is impregnated with a composition to produce aprecipitate that fills pore space. The aforementioned composition caninclude solutions, solid-phase fillers, ancillary reactants (solutionsand gases), and specific contaminant remediation agents (e.g., agentsfor petroleum products that are compatible with neutral to alkalineambient conditions such as alkali-silicate or metasilicate hydrocarbondegradation agents). Hereinafter, a metasilicate is defined as a salt ofmetasilicic acid and silicate is defined as a salt of silicic acid. Thiswaste zone impregnating step is repeated until refusal occurs. Theaqueous composition is selected from the group of:

CaCl₂ (solution)+Na₂CO₃ (solution),

CaCl₂ (solution)+Na₂SO,(solution),

CaCl₂ (solution)+Na₂HPO₄ (solution),

CaCl₂ (solution)+2NaOH (solution), and

FeCl₃ (solution)+3NaOH (solution)=3NaCl+Fe(OH)₃

The composition can also be a solution and a gas phase. In oneembodiment of the preceding group, the solution is 2NaOH+CaCl₂, and thegas phase is CO₂.

First, to achieve long term stability (i.e., as a natural analog(calcite)) the treatment is stable indefinitely in the presentgeological or physiochemical environment. After application, because ofresulting “self healing” properties within the ambient system, thetreated soil/rock will not fail because of rupture or stress fracturingsuch as occurs in concrete, degradation or flocculation (concrete, claycaps, and slurry walls), or external changes in the state ofoxidation/reduction (specific metal compound precipitates). NAS processproducts are stable, non-toxic analogs of naturally occurring minerals.

Second, to achieve self-healing, additional buffering and latentreactive capacity can be built into a specific application inanticipation of an unpredictable future activation, as an addedprotection. The treated site-system can be designed to be self-healingon a long term basis, or it can be designed to be gradually orcontinually implemented over time. Treatment additions or repairs toground missed during initial application are easily performed.

Third, to provide a solution to permeability reduction that iscommercially viable, the NAS process uses chemicals/preparations thatare readily available in bulk commercial lots; cost-per-ton formaterials is much less than cement. Waste zone permeation isproportional to void space (L+ water), not to the volume dilution (3:1and greater) required to make concrete. It is likely that applicationand engineering costs would dominate over the cost of materials in anycommercial scale project, in terms of cost of treated material, exceptfor projects where ground surface dispersal of the process treatmentmaterials or constituents that utilize meteoric water infiltration areappropriate (dry-mix, least expensive application).

Fourth, to provide a solution to permeability reduction that may beimplemented in otherwise untreatable waste sites, (i.e., in combinationwith directed drilling techniques such as navigational drilling, andgeophysical methods of monitoring underground injection), it is possibleto apply the NAS process to otherwise untreatable waste sites, such aswhere surface access is restricted, sealing beneath an existing landfillor dump, diverting groundwater flow, or treatments beneath bodies ofwater or in marine environments.

In addition, a further objective of this invention is to providesolutions to problems other than waste-site remediation. For example,the process can be used to stiffen or increase the cohesion of soilssubject to liquefaction such as in permafrost regions (e.g., road beds,building foundations) and seismic zones; as a slurry wall substitute inareas of salt water incursion where clay walls degrade; as acementatious fill in salt water environments wherein the product hardensand is stable indefinitely; as an admixture with coal/fly/incineratorash for disposal of the ash and/or its use to fill abandoned coal minesor other cavities or workings that are subject to collapse, or the useof the ash as a cementatious sluny; as an advanced preparation ofsubsoils in construction sites to mitigate the effects of future wastespills or storage (anticipatory remediation); as an injectablelow-viscosity sluny in construction applications using sand or otheradmixtures; and various other applications wherein the natural analogadvantage of the process is beneficial.

This technology emphasizes compatibility with ambient naturalconditions, and is a natural analog process; the results and predicteddurability of a treatment can be evaluated by comparison with naturalgeologic examples. The technology stiffens or solidifies soil/rockmasses in a way that is analogous to the natural formation ofsedimentary rock (lithification).

By using this technology, hazardous sites can be remediated in situ, bythe introduction of finely divided solids or slurries, or liquidchemicals, by injection with drilled pathways and installed pipes, byuse of seepage trenches, and/or by admixture of solid remediationcomponents, and/or by direct admixture of various components as bycommercial soil-mixing technologies. This avoids removal and off-sitetreatment and disposal of the waste/soil. The products of theremediation process are artificially produced analogs of naturallyoccurring substances or reaction breakdown products that are nothazardous.

Moreover, natural analog minerals can be caused to form during or afterremediation. Those minerals are insoluble in the ambient system andchemically bind toxic components such as Pb and Cr ions from the waste.Additionally, in this sense chemicals and elements can be introducedinto the waste during treatment that react in the waste zone and adsorbtoxic chemical species. For example, iron in solution can be introducedinto the waste zone and will then oxidize to produce Fe(OH)₂, a naturalanalog of the mineral limonite, that then adsorbs and chemically binds atoxic element such as chromium into this resultant insoluble mineral(limonite). These resultant minerals are called “designer minerals” inthat specific reactions and mineral products can be produced, during andafter application that bind, or “lock-up” specific toxic components thatare in the contaminated soil/waste.

This technology can also be used to treat sites in anticipation offuture events, for example, before they might become contaminated.Subsurface soil/rock of a site can be treated, for example, upon which achemical plant, petroleum refinery, factory, etc., is to be built. Thisis “anticipatory remediation” in that specific treatments to reduce oreliminate the permeability of a specific site can be introduced inanticipation of future use of the site. Anticipatory remediation wouldbe a general civil engineering/construction practice, usually involvingnonhazardous soil/rock that is intended to protect the subsurfaceenvironment in anticipation of contamination. Such contamination wouldinclude, but not be limited to, future spills of hazardous materials onthe treated site, accidental or otherwise.

Further use of this technology in the sense of anticipating futureevents involves the strengthening or solidification of soils/rocks byapplication of the process through admixture or injection of thechemical components that precipitate the carbonates or other products.For example, the technology can improve the stability of sites that aresusceptible to changes or damage caused by erosion, flooding, subsurfacewater-flow or human activities. Soil/rock slumping and mass wasting ofnatural and artificial slopes can be reduced or eliminated by thestiffening or solidification of the soil/rock. Such solidification ofsoil/rock in regions of permafrost or seasonal freezing that reduces oreliminates permeability of sub-surface water, would remediate theeffects of frost-heaving wherein water within soil bedrock freezes,expands, and causes subsurface and surface disturbance.

Examples of such applications are constructions of roadbeds, buildingfoundations, and aircraft landing strips. Yet another use of the processis to reduce or eliminate the permeability of soils that are susceptibleto soil liquefaction, induced by human or natural events. Examplesinclude soils that are susceptible to liquefaction during construction,or during use of constructions, such as roads and railways, and generalconstruction in fresh water, marine and shore-line environments thatinvolve saturated soils. In seismically active regions, or regions thatare otherwise susceptible to seismic energy, soils that are prone toliquefaction could be treated to reduce or eliminate permeability tosubsurface water and reduce or eliminate susceptibility to soilliquefaction.

The chemical remediation or treatment of waste sites operates byinducing chemical reactions or combinations of the waste components withmaterials that are added to, or impregnate, the waste in its host soilor matrix. The remediation effect also includes accompanying physicalchanges in the waste/host mass that act to support or enhance thechemically induced changes. In some applications the physical changesalone may be the primary remediation. The objective of chemicalremediation in any case, however, is to isolate, or prevent migration ofwaste components from the disposal site. Inasmuch as transportation inground or surface waters is the most common contaminant pathway forinorganic and many organic wastes, chemical remediation acts by a)altering waste components to insoluble or immobile forms that are stableunder natural ambient conditions, and b) reducing the permeability ofthe waste site, or sealing it in respect to the transmission of groundor soil water. This technique of remediation is applied on asite-specific basis that is tailored to the site conditions and wastecomposition. Both the materials used in chemical remediation and theapplication methods are specific adaptations of this general concept.

Chemical Effects

Chemical effects that are invoked in this new remediation technologyinclude:

precipitation from solution. For example:

Ca⁺⁺+CO₃ ⁻⁻═CaCO₃ (precipitate) as calcite cement.

Reactions between waste and added solutions yielding insoluble products.For example:

Pb⁺⁺+CO₃ ⁻⁻═PbCO₃;

Ba⁺⁺+Cr207-═BaCr₂O₇;

2Hg⁺⁺+Na2S2=2HgS+2Na⁺.

Adsorption of ions is effected by added adsorptants. For example: Pb⁺⁺adsorbed and chemically bound into Fe(OH)₂ or other basic ironhydroxy-oxides. Such adsorptants can be created by the use of FeCl₃solution in addition to the calcium ion solution, wherein exposure toalkaline pH will cause the precipitation of ferric hydroxide solid, aphase well known to adsorb heavy metals and effectively remove them fromfurther dispersal or migration, which subsequently flocculates toparticulate form (limonite or goethite, etc.). No oxidation reductionstep is needed, although ferrous iron solution certainly be used in aspecific case. For example:

FeCl₃═Fe(OH)₃ (sol or gel).

In some cases oxidation-reduction couples can yield a more insoluble orless toxic product. For example:

As⁵⁺+2HOH+3Fe°═As³⁺+Fe⁺⁺(FeOH)₂

6Fe⁺⁺+Cr₂0₇ ²⁻=Cr₂0₄ ²⁻+6Fe³⁺

Reactions can produce components known to occur as stable phases innature under the same ambient conditions. For example:

Ca(OH)₂+CO₂=CaCO₃+HOH;

Ca⁺⁺+SO₄ ⁻⁻═CaSO₄;

2Mg⁺⁺+HOH+CO₂═Mg₂(OH)₂C0₃ (basic magnesium carbonate).

Buffering capacity provided at the site helps complete reactions andprovides continued reaction capacity, and helps control pH.

Physical Effects

Physical changes that are intended to accompany a chemical remediationapplication include a reduction of soil/waste permeability and anincrease in soil/waste cohesion or consolidation as a result ofpore-filling and cementation/crystal growth enhancements. These changesare desired in order to restrict or inhibit the long-term access ofground/soil water to the waste, and any resultant leaching effects. Anexample of this is the NAS process which introduces a calcium carbonatematrix into the waste zone via application techniques that include:

a) Admixture of solid reactants with the waste, which subsequently reactin the presence of water (e.g., CaCl₂ and Na₂CO₃).

b) Admixture of finely particulate solid components that subsequentlycrystallize, react, or bond with the waste/soil (e.g., CaCO₃ as calciteor aragonite, Ca(OH)₂-hydrated lime, CaO-lime, and others). A variationof this technique with added matrix materials (e.g., fly ash,incinerator ash, cement kiln slag and ash, etc.) can be used to filllarger void spaces of coarse ground/waste materials such as gravels,coarse sands, waste debris, etc., found in abandoned mine workings.

c) Introduction or impregnation of the waste zone, which is waste andadmixed soil or overburden, with sequential solutions that react toproduce a precipitate that fills pore space (e.g., CaCl₂(solution)+Na₂CO₃ (solution)=CaCO₃ (precipitate)+2NaCl (solution loss toexternal soil/groundwater). This application of the solutions can berepeated until refusal occurs. Other examples of these solutions includeCaCl₂+Na₂SO₄═CaSO, (precipitate)+NaCl (solution); CaCl₂+Na₂HPO₄═Ca,(P0,)₂ (precipitate)+NaCl (solution).

d) Sequential solution-gas phase impregnation of the waste zone toproduce a calcium carbonate precipitate and cementing action, or result,as the reaction proceeds. For example:

2NaOH+CaCl₂═Ca(OH)₂(precipitate)+2NaCl(solution);

Ca(OH)₂+CO₂(introduced)=CaCO₃+2(OH⁻).

Another embodiment of this application is the admixture of solidhydrated lime or the introduction of slaked lime into the waste zoneprior to the introduction of CO₂. Yet another embodiment of the aboveremediation applications is the introduction of silica gel into thewaste zone as the pore filling agent. This can be accomplished viainfiltration or impregnation of an aqueous alkali-silicate ormetasilicate solution to which a suitable gelling agent (e.g., brinesalts) has been added at the point of solution introduction so thatgelation occurs after emplacement. However, to prevent dehydration ofthe gel, this embodiment is restricted mostly to wastes of acid pH atand within the saturated zone.

Example I

A specific example including the results of a field trial of thisinvention is shown below.

Sample and In-Situ Measurement Collection

Samples of “Solvay” waste (waste material produced by Solvay ProcessCorporation primarily from the production of soda ash) were collectedfrom the surface (upper 24 inches) Honeywell waste bed #14 in Syracuse,N.Y. Honeywell International is currently the over of the former Solvaywaste beds. The samples were hand collected and transported inpolyethylene-lined, five gallon pails that were sealed. At the time ofcollection in-situ measurements for moisture, wet density and drydensity were measured with a Troxler nuclear gauge (Troxler, 349 1-BSeries, Surface Moisture-Density Gauge) at the sampling site. Additionalmeasurements were made at approximately 20 meters from the sampling sitealong N-S, and E-W axes. Samples were collected Jun. 7, 2000. The GPScoordinates for the sampling site and field measurement sites, moistureand density measurements are given in Table 1.

TABLE 1 Honeywell waste bed sampling SITE SAMPLE WET DRY LOCATIONLOCATION MOISTURE¹ DENSITY² DENSITY² 43°03′95N 43°03′96N 118.6 76.7 35.176°15′70W 76°15′70W 43°03′95N 91.0 77.9 40.8 76°15′71W 43°03′95N 101.273.1 35.3 76°15′70W 43°03′95N 76°15′68W 85.8 74.0 39.8 43°03′95N76°15′69N 85.1 79.7 43.1 ¹Moisture by Dry Weight; ²lbs/Ft³

Standardized Testing

The NAS chemical process was tested for its ability to reduce thehydraulic conductivity of Honeywell waste bed material. The followingtesting methods and protocols were used in conducting the testing:

Laboratory Services:

-   -   Parrott-Wolff, Inc.    -   East Syracuse, N.Y. 13057 (Hydraulic Conductivity, Proctor        Tests)    -   Life Science Laboratory    -   East Syracuse, N.Y. 13057 (process solution preparation)

Analytical Methods:

ASTM D 5084-90: Standard Test Method for Measurement of HydraulicConductivity of Saturated Porous Materials Using a Flexible WallPermeameter;

ASTM D 89$: Test Method for Laboratory Compaction 10 Characteristics ofSnits Using Standard Effort (12.400 ft. lbs/ft³);

ASTM D 2922: Standard Test Method for Density of Soil and Soil-Aggregatein Place by Nuclear Methods (Shallow Depth); and

ASTM D 3017: Standard Test Method for Water Content of Soils and Rock inPlace by Nuclear Methods (Shallow Depth).

Equipment:

-   -   Troxler 3411-B Series Surface Moisture-Density Gauge; and    -   Brainard-Kilman E-4f10 Digital Transducer integrated with a        Trautwein Flexible-Wall Permeameter and Bladder Accumulator.

Process Fluids:

The specific chemical composition of the process fluids used in thetesting of the Natural Analog System are proprietary. Process fluid “A”is a carbonate source delivered at −85% saturation and Process fluid “B”is a calcium ion source delivered at 100% saturation.

Procedure Application

Sample # 14207C DATE PROCEDURES Sep. 5, 2000 The sample material wascompacted in accordance with ASTM D698 (Standard Compaction). The watercontent, at the time of compaction was 93.8 as a percent of dry weight.The dry density, after compaction, was determined to be 44.3 pcf. Sep.6, 2000 The sample was placed into the trixial confinement cell. A #200(0.074 mm) size stainless steel mesh screen was used in place of thetypical filter paper and porous stone, in order to avoid any falsepositive reduction in permeability due to clogging in the paper and/orstone. The sample saturation process began as backpressure was appliedby simultaneously increasing the cell pressure and the influent andeffluent pressures in 5 psi increments. During this incrementalprocedure, the influent and effluent pressures are kept equal while thecell pressure is maintained at 5 psi greater than the influent andeffluent pressures. During this procedure, regulated air pressure isapplied to a column of desired water. In turn, the deaired watertransfers the applied pressure to deaired process fluid (previouslydiluted to 85.0 percent saturation) across an impermeable flexiblemembrane. Ultimately the deaired process fluid applies the regulatedpressure to and into both ends of the confined sample. This replaces anyair in the influent and effluent lines, as well as any air filled poresin the sample, with the desired deaired fluid. 9/8/00 5:27 PM untilSaturation continued using the 9/12/00 2:45 PM deaired process fluid “A”solution until a B coefficient (saturation) of 98% was obtained in thesample (a minimum of 95% saturation is normally required). 9/12/00 3:01PM to An initial gradient of 30 was 3:42 PM then applied to the sampleto begin the test run using the process fluid as the influent. Forty-oneminutes after the test was begun, the first preliminary hydraulicconductivity was obtained and determined to be 1.8 × 10⁻⁵ cm/sec. Thehydraulic gradient was then reduced back to zero in order to temporarilyhalt the test. 9/13/00 7:OO PM to The initial gradient of 30 was 8:31 PMreapplied and a minimum of one void volume of process fluid(approximately 670 milliliters) was put through the sample. Thehydraulic gradient was then reduced back to zero in order to temporarilyhalt the test. A hydraulic conductivity was not obtained after anadditional 96 minutes of run time. 9/14/00 8:36 AM to The initialgradient of 30 was 4:11 PM reapplied. A second test run was begun andcontinued for 455 minutes. The second preliminary hydraulic conductiitywaas obtained and determined to be 5.1 × 10−4 cm/sec. The hydraulicgradient was then reduced bqack to zero in order to temporarily halt thetest. 9/20/00 8:00 AM to 9:50 AM The initial gradient of 30 wasreapplied. The test run was begun and continued for 110 minutes. A thirdpreliminary hydraulic conductivity was obtained and determined to be 3.4× 10⁻⁶ cm/sec. The hydraulic gradient was reduced back to zero in orderto temporarily halt the test. 9/22/00 8:13 AM to The initial gradient of30 was 8:43 AM reapplied and deaired process determined to be 1.2 × 10⁻⁶cm/sec. conductivity was obtained and preliminary hydraulic for 30minutes. A fourth preliminary hydraulic conductivity was obtained anddetermined to be 1.2 × 10⁻⁶ cm/sec. 9/27/00 8:42 PM to 5:59 PM Theinitial gradient of 30 was reapplied and the process fluid for 557minutes. A seventh test run was begun and continued the sample a secondtime. The “B” solution was introduced into the sample a second time. Thetest run was begun and continued for 557 minutes. A seventh preliminaryhydraulic conductivity was obtained and determined to be 3.9 × 10−7cm/sec. The hydraulic gradient was reduced back to zero in order totemporarily halt the test. 10/2/00 11:19 AM to 5:20 PM The initialgradient of 30 was reapplied. The test run begun and continued for 361minutes. An eighth preliminary hydraulic conductivity was obtained anddetermined to be 1.6 × 10−7 cm/sec. The hydraulic gradient was reducedback to zero in order to temporarily halt the test. 10/4/00 8:OO AM to10:30 AM The initial gradient of 30 was reapplied and the test run wasbegun and continued for 150 minutes. A ninth hydraulic conductivity wasobtained and determined to be 2.1 × 10⁻′ cm/sec. The hydraulic gradientwas reduced back to zero in order to temporarily halt the test. 10/5/008:05 AM to 12:35 PM The initial gradient of 30 was reapplied and thetest run begun and continued for four consecutive constant readings wereobtained. An end of test percent saturation of 98.0% was obtained. Theaverage final hydraulic conductivity was obtained and determined to be2.65 × 10⁻⁷ cm/sec. Oct. 6, 2000 The sample was removed from the celland photographed.

The results of the test on sample #14707C are graphically illustrated inFIG. 1, and shown in Table 2 in the Test Results Summary, below. A finalhydraulic conductivity value of 2.65×10⁻⁷ cm/sec was achieved with the“Solvay” waste sample #14207C.

Sample #14207D DATE PROCEDURES Sep. 5, 2000 The sample material wascompacted in accordance with ASTM D698 (Standard Compaction). The watercontent at the time of compaction was 99.5 as a percent of dry weight.The dry density after compaction was determined to be 41.8 pcf. Sep. 6,2000 The sample was placed into the trixial confinement cell. A #200(0.074 mm) size stainless steel mesh screen was used in place of thetypical filter paper and porous stone in order to avoid any falsepositive reduction in permeability due to clogging in the paper and/orstone. The sample saturation process began as backpressure was appliedby simultaneously increasing the cell pressure and the influent andeffluent pressures in 5 psi increments. During the incrementalprocedure, the influent and effluent pressures are kept equal while thecell pressure is maintained at 5 psi greater than the influent andeffluent pressures. During this procedure, regulated air pressure isapplied to a column of deaired water. In turn, the deaired watertransfers the applied pressure to of test percent saturation of 98.0%was obtained. The average final hydraulic conductivity was obtained anddetermined to be 2.12 × 10⁻⁵ cm/sec. Oct. 6, 2000 The sample was removedfrom the cell and photographed.

The results of the test on sample #14207D are graphically illustrated inFIG. 2, and shown in Table 2 in the Test Results Summary, below. A finalhydraulic conductivity value of 2.12×10⁻⁸ cm/sec was achieved with“Solvay” waste sample #14207D.

Test Results Summary

The Natural Analog System process was tested on “Solvay” waste collectedfrom a Honeywell wastebed in Central New York. Two samples were preparedand tested at the Parrot-Wolff Laboratories using standard ASTM testingprocedures. The goal of the testing was to determine the utility of theNAS process to effectively reduce permeability of ground, and reduce oreliminate leachate from waste beds and to remediate subsurfacecontamination plumes of chemical contaminants resulting from formerHoneywell chemical operations. Cementation of the host material wasachieved in a relatively short time. The results show a strong capacityfor the process to reduce permeability in the host material, effectivelyreducing water flow through and thus isolating the material from theenvironment.

Key Results

Test results show that the NAS process significantly reduced thehydraulic conductivity of the host material from 1.8×10⁻⁵ cm/second to2.65×10⁻¹ cm/second in approximately 550 hours for sample #14207C whichrepresents a 98.53% reduction. The values for sample #14207D were from1.8×10⁻⁵ cm/second to 2.12×10⁻⁸ cm/second in approximately 548 hourswhich represents a 99.88% reduction. It is noteworthy that both testswere terminated after hydraulic conductivities were reached that met orexceeded required values for remedial isolation technologies. It isexpected that hydraulic conductivities would continue to decrease andreach final values typical for the crystalline structure of thecementing compound, a natural analog of calcite. FIG. 3 shows themoisture-density curve (Proctor curve) with the relationship between thedry unit weight (density) and the water content of the waste materialfor a given compactive effort.

TABLE 2 Hydraulic Conductivity (k) Study Test Results And Timeline forTesting of Allied Waste Material Lab I.D. #14207C Lab I.D. #14207DHydraulic Hydraulic Cumulative Conductivity (k) Cumulative Conductivity(k) Elapsed Time (cm/sec) Elapsed Time (cm/sec) 0 Hours 1.8 × 10⁻⁵ 0Hours 1.8 × 10⁻⁵ 41 Minutes 41 Minutes 48 Hours 5.1 × 10⁻⁶ 47 Hours 9.9× 10⁻⁶ 24 Minutes 24 Minutes 185 Hours 3.4 × 10⁻⁶ 185 Hours 7.2 × 10⁻⁶16 Minutes 15 Minutes 233 Hours 1.2 × 10⁻⁶ 233 Hours 5.7 × 10⁶ 41Minutes 38 Minutes 239 Hours 8.3 × 10⁻⁷ 239 Hours 5.5 × 10⁻⁶ 41 Minutes9 Minutes 312 Hours 9.9 × 10⁻⁷ 312 Hours 2.2 × 10⁻⁶ 41 Minutes 48Minutes 362 Hours 3.8 × 10⁻⁷ 361 Hours 1.6 × 10⁻⁶ 41 Minutes 26 Minutes481 Hours 1.68 × 10⁻⁷ 481 Hours 2.71 × 10⁻⁸ 41 Minutes 4 Minutes 523Hours 2.07 × 10⁻⁷ 482 Hours 5.7 × 10⁻⁸ 41 Minutes 19 Minutes 549 Hours2.65 × 10⁻⁷ 548 Hours 2.12 × 10⁻⁸ 41 Minutes 19 Minutes

The waste zone is defined as a subsurface volume of ground, soil, or adump site, containing contamination in any physical form, which requiresremedial actions for site restoration. The remedial action pertains to asystem for the reduction of permeability in unconsolidated soils, overburden, fill and certain waste materials (the “ground”), or partlyconsolidated materials that can be excavated and broken up by normalearth moving and soil mixing equipment. The system permits theprevention or control of contaminant migration via groundwater flow orsurface water (precipitation) infiltration from a waste zone containingground wastes (other than garbage) of various types, thereby isolatingthese wastes. In some applications the system may also increase thecohesion and mechanical strength of unconsolidated ground in the wastezone.

A method of using the Natural Analog System (NAS) to reduce thepermeability of ground, wherein said ground is acidic (ambient pH lessthan 5), or contains wastes of pH 5 sufficient to render the groundacidic. If this condition is extensive, a modification of the NAS (asdescribed in claims above, is primarily applicable to ground at pH 5.5)is needed. Under acid conditions in nature, sediments are commonlycemented by some form of hydrated silica such as opaline silica, orcryptocrystalline chalcedony to fine grained quartz. This precipitationoccurs because silica is not soluble in acid solutions. The method ofusing the NAS in this context comprises the steps:

a) Impregnation of an underlayer of the ground, such as a waste zone,with an alkali-silicate or metasilicate solution, filling pore space ofthe underlayer of the ground or waste zone and reducing permeability andtransmission of fluids through the underlayer of the ground or wastezone because of the reduced pore space in the underlayer of the groundor waste zone. In some cases of high acidity, partial neutralization byaddition of a base in advance to the ground or waste zone, such asNa(OH) may be needed.

b) In the saturated zone of ground or waste zone, reaction or acidneutralization of the alkali-silicate or metasilicate solution in acidground will cause gellation and fixation of silica gel in void space,and thus reduce permeability.

c) In the unsaturated zone of ground or waste zone, or in some cases (b)of acid ground or waste zone which lacks sufficient soluble basic ions(Na, K, Ca, Mg, Ba, etc.) a suitable gelling agent (such as brinesolution) can be added at the point of impregnation to produce silicagel.

d) Repeat steps (a), (b), or (c) until refusal occurs.

e) Impregnation with an alkali-silicate or metasilicate solution canalso be applied to normal use NAS applications after precipitation ofCaC0₃ or Ca(OH)₂ to increase cohesion and mechanical strength of thetreated ground or waste zone.

The purpose of this invention is to provide a means of reducing thepermeability of “ground” to the transmission of natural groundwater,surface precipitation, or other non-acid aqueous fluids and waste waters(pH>4.5 on a long term basis). This reduction is accomplished bydecreasing the bulk connected intergranular void space in groundprimarily by the precipitation from solutions of pore filling chemicalconstituents similar to, or the same as, those occurring in theformation of sedimentary rocks from loose particle aggregates (soils,alluvium, water laid deposits, etc.). This formation occurs by thegrowth of chemical cements precipitated in pore space from groundwateror connate water; the most common by far being forms of calcium andcalcium-magnesium carbonates, and to a lesser extent, various forms ofsilica. Locally, other cements of the oxyacid salts (borates,phosphates, sulfates) may predominate. One example of this process ofpore filling cementation that occurs relatively rapidly geologically isthe formation of “caliche” deposits or cemented soils typical of the drylake beds of the arid SW United States. Such soils or soil zones can be10 ft. or more in thickness, and are virtually impermeable. Thisinvention aims to provide a means of artificially simulating thisprocess, and hence the name, Natural Analog System or NAS. Applicationsof the NAS include treatment of hazardous or toxic waste sites, in situ,to inhibit leachates in groundwater, 2) Pretreatment of ground toprevent subsequent contaminant migration, 3) Provide a barrier or sealedzone in ground to inhibit the transmission of groundwater.

A second aim of the NAS is to provide a means to immobilize, in situ,toxic metals and certain organics in waste (e.g. As,Cr,Hg,Ni,Cd,Pb,DNAPLs) in waste sites, upon or in the ground, to prevent theirtransmission to ground water via the percolation of surfaceprecipitation. Hereinafter, “DNAPL” is an acronym for “dense non-aqueousphase liquid”. For this purpose reactants that form insoluble compoundswith, or adsorb, toxics, such as ferric hydroxide sols are added orproduced in the NAS process.

A third aim is a means of sealing and stabilizing acid leachategenerating waste materials as are found in some slag heaps, and as couldbe used as fill in abandoned coal mines. A modification of theprecipitation process in applications to unconsolidated ground or soilcan be used to develop mechanical strength or enhance rigidity followingtreatment, e. g. as in road base preparation, barrier walls, and earthfill levees (i.e. add sodium silicate or metasilicate solution).

A Natural Analog System (NAS) method to reduce the permeability ofacidic, neutral, or alkaline (pH>3) ground by:

a) the precipitation of insoluble alkaline earth-oxyacid salts that fillpore space and thus inhibit fluid transmission.

b) In more acid ground (pH<3) unsuitable for neutralization and alkalinebuffering, the precipitate to reduce permeability will be a form ofsilica derived by the gellation of alkali-silicate or metasilicatesolutions.

c) A secondary effect of this precipitation, alone or by reaction withother constituents, is to increase the cohesive or mechanical strengthof the ground. The reaction constituents may the original components ofthe ground, or added (impregnated) subsequently.

d) An application of the NAS method to a predetermined ground isdependent upon at least one characteristic of the said ground determinedby physical measurement or chemical analysis of: Initial hydraulicconductivity, configuration or potentiometric surface, bulk chemistry,hydrochemistry, or ether physical properties.

e) The predetermined ground may be a waste zone and chemical analysismay be of hazardous, toxic, or regulated constituents or contaminants.

f) The method of using the NAS as in (a) by impregnating the ground witha solution of a soluble alkaline earth salt (e.g. CaCl₂) and a solutionof a soluble oxyacid salt (e.g. Na₂CO₃) which then react to an insolubleprecipitate (CaCO₃ in this example) in pore space of the ground. Saidoxyacid salt solutions and precipitates are selected from the group:

CaCl₂ (soln)+Na₂CO₃═CaC0₃ (ppt.)  Reaction A

CaCl₂ (soln)+Na₂SO₄═CaSO₄

CaCl₂ (soln)+Na₂HPO₄═Ca₃(PO₄)₂

CaCl₂ (soln)+2NaOH═Ca(OH)₂  Reaction B

2CaCl₂+Na₂CO₃+2NaOH=CaCO₃+Ca(OH)₂(mixed ppt.)A+BFeCl₃+3NaOH═Fe(0H)₃(sol)

(all precipitates are accompanied by by-product NaCl solution which islost or expelled upon compaction of ground).

g) The method of using NAS as in (c) where the ground is of acid pH andthe solution is sodium or potassium-silicate or metasilicate (SS) andthe gellation agent is brine salts.

h) The method of using NAS as in (c) where the added constituents areselected (one or more) from hydrated lime, Ca(OH)₂ (solid), Na₂SiO₃ orK₂SiO₃ alkali solutions (SS), high calcium fly ash (solids), H₂C0₃(solution), and C0₂ (gas) to order to increase cohesion orsolidification of the ground.

i) Examples of applications of the NAS in respect to pH of ground anddesired cohesion or plasticity following impregnation (f), (g), or (h)are tabulated in FIG. 4. All quantities of solutions assumeconcentrations near saturation and approximate equal stoichiometry inreactions for maximum efficiency. Letter abbreviations refer toreactions or components in (f), (g) above. A, B, and reactions in part(f) operate in neutral to alkaline media, or (SS) are alkaline. pH<3 inground require additional alkaline buffering, as by NaOH. and/or SS toneutralize acidity.

DEFINITION OF TERMS

(SS) includes part (h) and may be applied to any tabulation above,before, or after the NAS method, as determined by on site hydraulicconductivity measurements of the ground or waste zone.

Reaction (A) usage includes sulfate and phosphate anion options, asdetermined by ground or waste zone characteristics.

“Plastic” refers to a relative state of consolidation of ground afterNAS treatment; a condition able to prevent flowage or liquifaction inunconsolidated deposits subject to seismicity, but not rigid to thepoint of failure by rupture. Another application is barrier walls togroundwater flow in the ground.

“Cohesive” refers to a state of consolidation or soil fixation assuitable for subpavement or road base, earthen levees, and similarapplications.

In one embodiment of a method of enhancing a use of a Natural AnalogSystem (NAS) waste in a waste zone is analyzed to identify chemicalconstituents for which immobilization is particularly desirable.

In a step of the method of enhancing a use of a Natural Analog System(NAS), the waste zone is impregnated with a known increment of asuitable solution equal to or greater than the calculated amountrequired to react with said chemical constituents, wherein the suitablesolution comprises iron in solution. In a step of the method ofenhancing a use of a Natural Analog System (NAS), the chemicalconstituents of the waste are selectively immobilized as insoluble solsformed from said chemical constituents and the suitable solutions. In alast step of the method of enhancing a use of a Natural Analog System(NAS), the analyzing, impregnating and selectively immobilizing stepsare repeated until refusal occurs.

Hereinafter, “enhancing a use of a Natural Analog System (NAS)” isdefined as selectively immobilizing the contaminants. A reaction betweenadsorptants, such as iron salts, and contaminants such as As, Pb, Cr,Cd, and/or Ni, in their ionic forms, immobilizes the contaminants.Adsorption of ions is effected by added adsorptants. For example:

FeCl₃═Fe(OH)₃ (sol or gel).

Such adsorptants can be created by the use of FeCl₃ solution in additionto the calcium ion solution, wherein exposure to alkaline pH will causethe precipitation of ferric hydroxide solid, a phase well known toadsorb heavy metals and effectively remove them from further dispersalor migration, which subsequently flocculates to particulate form(limonite or goethite, etc.). No oxidation reduction step is needed,although ferrous iron solution certainly be used in a specific case. Forexample: Pb⁺⁺ adsorbed bound into Fe(OH)₂ or other basic ironhydroxy-oxides.

In some cases oxidation-reduction couples can yield a more insoluble orless toxic product. For example:

As⁵⁺+2HOH+3Fe°═As³⁺+Fe⁺⁺(FeOH)₂

6Fe⁺⁺+Cr₂0₇ ²⁻=Cr₂0₄ ²⁻6Fe³⁺

The reaction precipitate iron hydrozide sols of the As, Pb, Cr, Cd,and/or Ni contaminants, wherein the contaminants are immobilized bychemical adsorption.

In one embodiment of the method of enhancing a use of a Natural AnalogSystem (NAS), the iron is selected from the group consisting of Fe⁰,Fe⁺⁺ and Fe³⁺ and combinations thereof.

In one embodiment of the method of enhancing a use of a Natural AnalogSystem (NAS), the chemical constituents comprise lead, and the suitablesolution comprises carbonic acid.

In one embodiment of the method of enhancing a use of a Natural AnalogSystem (NAS), the chemical constituents comprise mercury, and thesuitable solution comprises sodium sulfide.

In one embodiment of the method of enhancing a use of a Natural AnalogSystem (NAS), the chemical constituents comprise chromate ion (Cr₂0,⁻⁻),the suitable solution comprises barium ion (Ba⁺⁺).

In one embodiment of the method of enhancing a use of a Natural AnalogSystem (NAS), the chemical constituent comprises a member of the groupincluding lead, arsenic, mercury, chromium, and cadmium, the suitablesolution including ferric chloride.

In one embodiment of the method of enhancing a use of a Natural AnalogSystem (NAS), the waste zone comprises at least one of the group:gravels, coarse sands, and waste debris found in abandoned mineworkings.

In one embodiment a method of using a Natural Analog System (NAS) toreduce the permeability of an acidic ground or waste zone, comprises astep of impregnating the ground or waste zone with an alkalineearth-oxyacid salt or an alkali-silicate or metasilicate solution. Thereaction of acid with the alkali-silicate or metasilicate results inSiO₂ precipitating, filling pore space in an underlayer of the ground orwaste zone and reducing permeability and transmission of fluids in theunderlayer of the ground or waste zone because of the reduced porespace. In this embodiment, the impregnating step is repeated untilrefusal occurs. A role of the alkali-silicate or metasilicate solutionis to act as a buffer in the presence of the acidic waste zone.Alternatively, the alkali-silciate solution may be represented asvarious forms of silica (Si0₂ or SiO_(X)(H₂O)_(y)) as compatible inambient alkaline or acid environments, respectively.

In one embodiment of the method of using the Natural Analog System (NAS)to reduce the permeability of the acidic waste zone, the acidic wastezone is impregnated with an alkaline earth-oxyacid salt if the pH of thewaste zone is greater than 3.

In one embodiment of the method of using the Natural Analog System (NAS)to reduce the permeability of the acidic waste zone, the acidic wastezone is impregnated with an alkali-silicate or metasilicate solution ifthe pH of the waste zone is less than 3

In one embodiment of the method of using a Natural Analog System (NAS)to reduce the permeability of the acidic waste zone, a brine solution isadded at the point of impregnation to produce silica gel.

In one embodiment of the method of using a Natural Analog System (NAS)to reduce the permeability of the acidic waste zone, the acidic wastezone is partially neutralized by addition of Na(OH) before impregnatingthe ground or waste zone with an alkaline earth-oxyacid salt or analkali-silicate or metasilicate solution.

In one embodiment of the method of using a Natural Analog System (NAS)to reduce the permeability of the acidic waste zone, impregnating thewaste zone with the alkaline earth-oxyacid salt comprises impregnatingthe waste zone with a solution of a soluble alkaline earth salt and asolution of a soluble oxyacid salt, which then react to an insolubleprecipitate in the pore space of the ground.

In one embodiment, a method of using a Natural Analog System (NAS) toreduce the permeability of ground, wherein said ground contains wastessuch that the pH of said ground is acidic, and wherein said ground lieswithin a saturated waste zone, comprises a step in which the waste zoneis impregnated with a composition to produce gelation, filling porespace, said composition comprising an aqueous alkali-silicate ormetasilicate solution.

In one embodiment of this method of enhancing a use of a Natural AnalogSystem (NAS), a suitable gelling agent is added at the point of saidsolution introduction, thereby inducing gelation, producing silica gel.In this method, the impregnating step is repeated until refusal occurs.

In one embodiment of the method of enhancing a use of a Natural AnalogSystem (NAS) to reduce the permeability of ground the suitable gellingagent comprises brine salts.

In one embodiment, a Natural Analog System to reduce the permeability ofacidic, neutral, or alkaline (pH>3) ground comprises a step ofprecipitating insoluble alkaline earth-oxyacid salts that fill porespace and thus inhibit fluid transmission. An example of an alkalineearth-oxyacid salt is CaCO₃.

In one embodiment, a Natural Analog System to reduce the permeability ofacidic (pH<3) ground, which may be unsuitable for neutralization andalkaline buffering, comprises a step of impregnating the ground with aform of silica derived by the gellation of alkali-silicate ormetasilicate solutions, and precipitating the silica to reducepermeability. A secondary effect of this precipitation, alone or byreaction with other constituents, is to increase the cohesive ormechanical strength of the ground. The reaction constituents may beoriginal components of the ground, or added (impregnated) subsequently.

In one embodiment, a method of enhancing the use of the Natural AnalogSystem (NAS) to reduce the permeability of ground, wherein certainchemical constituents of the waste are selectively immobilized,producing insoluble reaction products between said chemical constituentsand suitable solutions, the steps comprising a step of a) analyzingwaste to identify chemical constituents for which immobilization isparticularly desirable; and b) impregnating said waste with a knownincrement of said suitable solutions equal to or greater than thecalculated amount required to react with said chemical constituentsforming insoluble reaction products.

In one embodiment, the method of enhancing the use of the Natural AnalogSystem (NAS) to reduce the permeability of ground, by selectivelyimmobilizing certain chemical constituents of waste, insoluble reactionproducts are produced between the chemical constituents and suitablesolutions. The chemical constituent may include lead, and the suitablesolution may include carbonic acid.

In one embodiment of the method of enhancing the use of the NaturalAnalog System (NAS) to reduce the permeability of ground, by selectivelyimmobilizing certain chemical constituents of waste, insoluble reactionproducts are produced between said chemical constituents and suitablesolutions. The chemical constituents may include mercury, the suitablesolution including sodium sulfide.

In one embodiment, the method of enhancing the use of the Natural AnalogSystem (NAS) to reduce the permeability of ground, by selectivelyimmobilizing certain chemical constituents of waste, insoluble reactionproducts are produced between said chemical constituents and suitablesolutions. The chemical constituents may include chromate ion (Cr₂0₇⁻⁻), the suitable solution may include barium ion (Ba⁺⁺)

In one embodiment, the method of enhancing the use of the Natural AnalogSystem (NAS) to reduce the permeability of ground, by selectivelyimmobilizing certain chemical constituents of waste, insoluble reactionproducts are produced between said chemical constituents and suitablesolutions. The chemical constituents may comprise a member of the groupincluding lead, arsenic, mercury, chromium, and cadmium, the suitablesolution may include ferric chloride.

Since other modifications and changes varied to fit particular operatingrequirements and environments will be apparent to those skilled in theart, the invention is not considered limited to the examples chosen forpurposes of disclosure and covers all changes and modifications which donot constitute departures from the true spirit and scope of theinvention.

Having thus described the invention, what is desired to be protected byLetters Patent is presented in the subsequently appended claims: 1-20.(canceled)
 21. A method for introducing a calcium carbonate matrix intoa waste zone via application techniques, comprising: admixing solidCaCl₂ and Na₂CO₃ with the waste zone, which subsequently react in thepresence of water.
 22. A method for introducing a calcium carbonatematrix into a waste zone via application techniques, comprising:admixing a finely particulate solid selected from the group consistingof CaCO₃ as calcite or aragonite, Ca(OH)₂-hydrated lime, and CaO-limethat subsequently crystallize, react, or bond with waste/soil in thewaste zone.
 23. The method of claim 22, comprising: adding matrixmaterials selected from the group consisting of fly ash, incineratorash, cement kiln slag, and cement kiln ash to fill larger void spaceswhen the waste/soil is coarse ground/waste materials.
 24. The method ofclaim 23, wherein the coarse ground/waste materials are selected fromthe group consisting of gravels, coarse sands, and waste debris.
 25. Themethod of claim 24, wherein the coarse ground/waste materials are foundin abandoned mine workings.